Sleep-Crashing

In any of the equine behavior literature that I have read, I am unable to find any description of the sleeping behavior we see in our retired broodmare (17 years old). She has functioned as the watch horse in the small herd she was from, and she now is retired at our two-horse farm and continues to maintain that role. She is rarely seen lying down, nor shows evidence of that--no surface dirt or shavings in her coat. She does not prefer to rest inside the run-in barn stall (if she does, it is always with her head facing out), but is often seen sleeping standing up just outside of the barn and stall door of the second horse as he sleeps lying down inside.

Often I have seen her resting, head drooping lower and lower over straight parallel forelegs (with a rear leg cocked in relaxation fashion). However, sometimes after a few minutes of what appears to be deeper sleep, her forelegs begin to buckle at the pastern and knee joints. As she begins to go down, she wakes up in a sudden jerking motion, lifting her head, then all is fine. However, I have suspected that she falls occasionally onto a foreleg during times of sleep as evidenced by dirt or shavings only on the anterior surface of a knee, the cannon bone area, and the long pastern. The opposite leg has excess dirt or shavings over the long pastern area.

She is often very grumpy when touched in the shoulder and chest area. (Is she sore?) This behavior has been attributed to past experience with saddling, but the ears back and half-hearted nip directed to the handlers approaching a hand or light touch at that area occurs with or without the presence of a saddle or saddle-related human behaviors (placing riding equipment and grooming supplies, positioning, etc.). Through clicker training she has substituted a head down response for the nip action, most of the time.

The other day, there was finally confirmation to my suspicion when I saw her while dozing, fall down onto her knees, wait a moment while organizing herself, then pulling her front end back up again to a normal standing position. Her hind legs continued to support her hind end. It seems like that activity could create legitimate shoulder soreness.

Is that kind of falling normal for an older horse that sleeps standing up? She has no lameness problems, doesn't have stumbling problems when ridden, and otherwise appears healthy. Is it significant? I have had my veterinarian examine her for front end soreness and nothing was found, although I did not mention that she falls on her front end while sleeping because at that point I was only guessing it might happen. Have you ever seen anything like that in your experience of sleeping horses? Joan

Yes, I have seen the behavior you describe. It is not considered normal, and it can be significant. There can be a couple of things going on that should be evaluated. The simplest is a problem seen when the horse is just not comfortable lying down and/or getting up. It can happen to otherwise normal horses who are confined in too small of a tie-stall, too short of a tether in a tie-stall, or slippery footing so they are not physically able to lie down. In the case of discomfort, it is more commonly seen in older horses just because they tend to have arthritis or other musculoskeletal issues that would impede efficient getting down and rising after recumbency.

If you obtain and view some 24-hour video tape samples of such horses, you can see that they will be in many cases observed trying to lay down. You might seem them circle and paw at a spot where they are about to lie down, even looking "longingly" to lie down, but then don't proceed. Or they might start to tuck their legs under and crouch, but stop part way down. Or they might plop down, rest, then struggle to get up. From viewing the video, you can often also get insight into what could be bothering the horse or interfering either with the lying down and/or getting up.

Horses having such difficulty can go for very long periods, even months, without lying down. They just sleep standing. When a horse goes a long time without lying down, it tends to do what you describe, which is break at the knees when it goes sound asleep standing up. This might be because the horse tends to go into a deeper sleep than a normal standing sleep.

I would recommend videotaping signs of this problem and looking for clues asto the location of the discomfort, with the goal of trying to address any signs of musculoskeletal discomfort. We just put a camera on a tripod and video on SLP mode so that a two-hour tape becomes six hours. You can get longer playing VHS tapes so you can get 10 hours before changing the tape.

If you can't find any problems, you might try some deep bedding. Horses that have trouble going down, in other words have been "falling" hard as they try to lie down, usually seem to appreciate a soft bed that will cushion the "plop." If the problem includes difficulty rising, you want to be sure there is good footing to make it as easy as possible. When she is outside on good sod, she might do better than in a stall.

Even though she is not lame, you might find that she will get some benefit from pain medication, say a light dose of phenylbutazone. Also, any joint health supplements that your veterinarian can recommend could be helpful with time.

Another, more rare reason, for such behavior is a neurologic/central nervous system disorder. Narcolepsy is one such disorder, but there are variations of that sleep disorder, as well as other neurologic conditions that cause changes in mentation resulting in behavior somewhat similar to what you describe.

In classic narcolepsy, the horse goes from normal alertness to deep standing sleep, falls to its knees, which wakes it, deep sleep, falls, in very rapid cycling. The big difference between narcolepsy and falling asleep too deeply when standing is the very rapid cycling between high arousal to deep sleep. It ends up being quicker and more violent than for horses such as yours. In fact, in narcolepsy the horse might respond to increased excitement by sudden deep sleep. You might be getting the horse saddled and it falls asleep as it gets excited. The nicks and dings on the knees are usually more severe in narcoleptic horses, and there are often injuries on their heads and other parts of their bodies depending upon how hard they fall before they are alert again.

Horses with sleep disorders and other neurologic or central nervous system problems, however, usually do have normal recumbent sleep. The sleep disorder occurs just during the normal periods of standing rest.

Your horse sounds like she starts with a period of normal standing rest, then normal drowsiness, then deeper standing sleep, and not always deep enough to buckle to the knee. A veterinary work-up is recommended, since some seizures and cardiac-related weakness (and other rare conditions) can have similar signs.

On the grumpiness and sensitivity to touch, no matter why a horse is dropping to its knees, you're right that there would likely be secondary aches and pains. The shoulder, the forelimbs, and the abdominal muscles could get sore fast. You can see how this can get to be a vicious cycle--the additional injuries and soreness wouldn't make getting up and down any easier.

The grumpiness might also be related to the root cause (whatever hurts initially) that is interfering with getting up and down for normal recumbent rest. Also, long-term sleep deprivation, particularly of the deep REM sleep that horses get only when they lie down, theoretically could cause temperament changes. In actual experience with some horses that I knew long-term that were not lying down, I did not see significant general temperament changes.

You refer to your horse as the watch-horse. Are you suggesting that maybe your horse is reluctant to lie down because of her sentinel duties? That's an interesting question.

In my experience, except in very threatening environments, the apparent need for recumbent rest seems to eventually become important enough that even the most vigilant sentinel horse lies down and either the herd mate stays alert during that time, or they both conk out at a quiet moment.

About the Author

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

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